全文获取类型
收费全文 | 44420篇 |
免费 | 498篇 |
国内免费 | 345篇 |
专业分类
安全科学 | 1386篇 |
废物处理 | 2067篇 |
环保管理 | 5963篇 |
综合类 | 7028篇 |
基础理论 | 11969篇 |
环境理论 | 18篇 |
污染及防治 | 10989篇 |
评价与监测 | 2973篇 |
社会与环境 | 2582篇 |
灾害及防治 | 288篇 |
出版年
2022年 | 347篇 |
2021年 | 416篇 |
2020年 | 276篇 |
2019年 | 330篇 |
2018年 | 595篇 |
2017年 | 654篇 |
2016年 | 1002篇 |
2015年 | 728篇 |
2014年 | 1150篇 |
2013年 | 3601篇 |
2012年 | 1395篇 |
2011年 | 1892篇 |
2010年 | 1553篇 |
2009年 | 1603篇 |
2008年 | 1945篇 |
2007年 | 1926篇 |
2006年 | 1720篇 |
2005年 | 1526篇 |
2004年 | 1468篇 |
2003年 | 1418篇 |
2002年 | 1338篇 |
2001年 | 1616篇 |
2000年 | 1160篇 |
1999年 | 690篇 |
1998年 | 548篇 |
1997年 | 585篇 |
1996年 | 603篇 |
1995年 | 707篇 |
1994年 | 617篇 |
1993年 | 555篇 |
1992年 | 564篇 |
1991年 | 553篇 |
1990年 | 544篇 |
1989年 | 524篇 |
1988年 | 482篇 |
1987年 | 427篇 |
1986年 | 397篇 |
1985年 | 401篇 |
1984年 | 461篇 |
1983年 | 416篇 |
1982年 | 474篇 |
1981年 | 395篇 |
1980年 | 311篇 |
1979年 | 348篇 |
1978年 | 309篇 |
1977年 | 267篇 |
1975年 | 251篇 |
1974年 | 251篇 |
1973年 | 288篇 |
1972年 | 261篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
A fragment constant QSAR model for evaluating the EC50 values of organic chemicals to Daphnia magna.
Shu Tao Xiaohuan Xi Fuliu Xu Bengang Li Jun Cao R Dawson 《Environmental pollution (Barking, Essex : 1987)》2002,116(1):57-64
The quantitative relationship between the median effective concentration (EC50) of organic chemicals to Daphnia magna and the number of molecular fragments was investigated based on experimental EC50 values for 217 chemicals derived from the literature. A fragment constant model was developed based on a multivariate linear regression between the number of fragments and the logarithmically transformed reciprocal values of EC50. Functional correction factors were introduced into the model. The model was verified using an independent set of randomly selected data. The mean residual of the final model was 0.4 log-units. The robustness of the model was discussed based on the results of three jackknife tests. 相似文献
12.
13.
14.
A transition zone in the otoliths of orange roughy (Hoplostethus atlanticus) is described where annulus width decreases markedly. For fish sampled at spawning time, the relationship between gonad stage
and the presence or absence of a transition zone is consistent with the hypothesis that this zone marks the onset of maturity,
if allowance is made for some error in gonad staging and identification of the zone. Another data set from a non-spawning
area after the spawning season is not consistent with the hypothesis. However, these latter data are considered less reliable
because of the small size of the fish in the sample and difficulties in determining, outside the spawning season, whether
a fish has been reproductively active. This hypothesis was used to provide estimates of the median age (30 yr) and length
(31 cm) at the onset of maturity for the Chatham Rise, New Zealand population. These estimates are unaffected by the biases
associated with the usual ogive method of estimation.
Received: 27 June 1997 / Accepted: 1 July 1997 相似文献
15.
16.
17.
18.
19.
Molecular phylogeny and population structure of tideland snails in the genus Cerithidea around Japan
Phylogenetic relationships and genetic population structures were analyzed for tideland gastropods in the genus Cerithidea around Japan on the basis of partial sequence of the mitochondrial COI gene. Large genetic divergence was shown between individuals of Cerithidea cingulata in the southern Ryukyus and those in the central Ryukyus and the Japanese Islands. Haplotypes of C. cingulata from the Japanese Islands were paraphyletic with the exclusion of a monophyletic group from the central Ryukyus. Genetic differentiation of C. cingulata was also detected between Amami-Oshima Island and Okinawajima Island. No genetic divergence was found between Cerithidea rhizophorarum in the Japanese Islands and its subspecies C. rhizophorarum morchii in the Ryukyu Islands. The lack of genetic divergence of Cerithidea largillierti between continental China and Japan suggests relatively recent migration between the Japanese Islands and the Asian continent. For all three Cerithidea species distributed in both the Japanese Islands and the Ryukyu Islands, the Tokara Gap and the Kerama Gap were shown to have acted as barriers to the dispersal. 相似文献
20.